Wheat germ is a by-product of wheat flour milling, and it is the most physiologically active part of wheat grains, and its content accounts for 2% to 3% of the weight of wheat grains. Wheat germ contains a variety of nutrients, such as germ protein, germ oil, vitamins, minerals, etc., and is known as a natural treasure trove of nutrition.
Wheat germ oil
Wheat germ oil accounts for about 10% of the dry weight of wheat germ. Because it is rich in many unsaturated fatty acids, vitamin E, linoleic acid, octacosanol, phospholipids, and some fat-soluble pigments, it is of very high quality. Wheat germ oil is a kind of advanced nutritional health care oil. Its main function is to improve the functional state of the body.
The CO2 extraction method of wheat oil
Weigh 500g of crushed wheat germ powder into a 1L extraction kettle, set each process parameter of supercritical COB2B extraction, and open the heating device of the refrigeration device, extraction kettle, and separation kettle.
When each temperature reaches the set value, turn on the carbon dioxide pressurizing pump to pressurize to the required extraction pressure, adjust the flow of COB2B to be constant, and cycle the extraction. The pressure of the fixed separation kettle was 5.5 MPa, and the separation temperature was 40°C.
CO2 supercritical extraction process: wheat germ—weighing—charging in the extraction kettle—sealing—heating, boosting—CO2 cycle—extraction—depressurizing—collecting—wheat germ oil.
4 Keys Affecting CO2 Extraction Efficiency
The extraction temperature was fixed at 45℃, the particle size of the wheat germ was 100 mesh, and the extraction time was 2h. The extraction was carried out under pressure conditions of 20, 22, 25, 28, 30, and 35 MPa, and the experiment was repeated three times.
The yield of wheat germ oil increased with pressure. Increase and increase, the yield does not change greatly with the increase of pressure at 20-25MPa; but after 25MPa, the yield of 25-30MPa wheat germ oil increases from 8.3% to 11.4%, the yield increases significantly; The yield of 30-35MPa wheat germ oil increased from 11.4% to 11.6%, with almost no significant changes.
How to choose the pressure
Extraction pressure is one of the important parameters affecting supercritical carbon dioxide extraction.
The effect of extraction pressure on supercritical carbon dioxide extraction is mainly achieved by changing the density of carbon dioxide. Because the solubility of supercritical carbon dioxide is proportional to its density, the density of carbon dioxide directly affects its ability to dissolve grease.
Within the range of soluble pressure (that is, the pressure at the beginning of dissolution) and the maximum pressure, the extraction pressure increases, the density of CO2 also increases, and the extraction rate of oil and fat will increase accordingly.
However, there is not a linear relationship between the extraction pressure and the oil extraction rate. When the extraction pressure increases to a certain degree, the dissolution capacity increases slowly, so the increase in the CO2 dissolution capacity and oil extraction rate decreases. However, with the increase in extraction pressure, the cost of equipment and operating costs have increased accordingly, increasing investment costs. Therefore, 30MPa is the optimization extraction pressure for extracting wheat germ oil.
With a fixed extraction pressure of 30 MPa, a wheat germ particle size of 100 mesh, and an extraction time of 2 hours, the extraction was carried out at temperatures of 40, 45, 50, and 55°C, and the experiment was repeated three times. In the beginning, the yield of wheat germ oil increased with increasing temperature Gradually increase, the maximum yield is 11.4% when the temperature reaches 45 ℃, after 45 ℃, the yield at 50 ℃ is 10.8%, and the yield at 55 ℃ drops to 10.2%, the yield of volatile oil decreased with the increase of temperature.
Temperature is also an important factor affecting the density of CO2, and the greater the density of CO2, the greater its solubility in grease. Under a certain extraction pressure, the higher the temperature, the lower the density of CO2, and the worse the dissolving ability.
Therefore, when the temperature exceeds a certain value, the extraction rate of wheat germ oil decreases instead.
In addition, the critical temperature of CO2 is 31.2°C. When the temperature is lower than this critical value, the solubility of CO2 to grease becomes lower. Therefore, the general extraction temperature must be higher than the critical temperature of CO2.
From the experimental data, the extraction temperature of 45 ℃ is the optimization temperature for extracting wheat germ oil.
Pulverized particle size
Fixed extraction pressure 30Mpa, extraction temperature 45℃, extraction time 2 hours, extraction under wheat germ particle size of 60 mesh, 80 mesh, 100 mesh, 120 mesh, repeat the experiment three times, the yield of wheat germ oil with different particle sizes is also different when the particle size is 60 mesh, the yield is only 7.7%, 80 mesh is 8.9%, the maximum yield at 100 mesh is 11.4%, and 120 mesh is 11.6%.
Particle size is also an important factor affecting the extraction rate.
It can be seen from the experimental data that the particle size increases from 60 mesh to 100 mesh, and the oil yield is significantly increased but exceeds 100 mesh. Due to the fine powder, the extracts are too densely contacted with each other, and there is no gap, which will aggravate the carbon dioxide fluid and materials.
The thermal effect of the interface increases the bulk density of the material and deteriorates the permeability.
As a result, CO2 gas only passes through the material layer along the line with low resistance, forming many pinholes, and at the same time, it quickly forms a dense hard block under the pressure.
The extracts hardened, and the yield decreased significantly. Similarly, if the particle size is too coarse, the contact area between the material and the CO2 gas decreases, the extraction speed becomes slower, and the extraction amount decreases.
Therefore, combined with the experimental data, it is concluded that when the wheat germ particle size is 100 mesh, it is the optimization extraction particle size.
The wheat germ with a fixed extraction pressure of 30 MPa, extraction temperature of 45°C, and a particle size of 100 mesh were collected at 0.5, 1.0, 1.5, and 2.0 h time points.
The experiment was repeated three times and the yield of volatile oil was calculated.
The yield of volatile oil increased with time. Gradually increasing, the yield increases rapidly at 0.5-1.5h, and the yield-extraction time curve changes almost linearly.
By 1.5h, it has reached 11.2%. After 2h, there is almost no product, and the yield remains basically unchanged. Therefore, in order to improve efficiency and save energy, the appropriate time is 1.5h.
Through multiple experiments, the various parameters of supercritical carbon dioxide extraction of wheat germ were studied and analyzed. According to the experimental results, the optimization process parameters of supercritical carbon dioxide extraction of wheat germ oil can be obtained: extraction pressure 30MPa, extraction temperature 45℃, extraction time At 1.5h, the wheat germ size is 100 mesh. Under this condition, the yield of wheat germ oil is 11.2%. This result provides a good theoretical basis for the industrial production of wheat germ oil.
CO2 extraction process of wheat oil
The wheat germ was extracted using supercritical CO2 extraction technology. Taking the yield of wheat germ oil as the index of investigation, the effects of extraction pressure, temperature, time, and wheat germ particle size on the extraction of wheat germ oil by supercritical CO2 fluid were investigated.
The results show that the extraction pressure is 30MPa, the extraction temperature is 45℃, and the wheat germ particle size is 100 mesh. The extraction process is 1.5h, which is the optimization process.
The yield of wheat germ oil is 11.2%.
- Pulverization degree:100 mesh
- Extraction pressure: 300 bar
- Extraction temperature: 45°C
- Separation pressure: 90 bar
- Separation temperature: 53°C
- Extraction time: 90 min
Wheat germ is a by-product of wheat flour milling, and it is the most physiologically active part of wheat grains, and its content accounts for 2% to 3% of the weight of wheat grains.
Wheat germ contains a variety of nutrients, such as germ protein, germ oil, vitamins, minerals, etc., and is known as a natural treasure trove of nutrition.